High frequency electric discharge device



m, 9 20w wV//// 5 .Q t M MNA-MM 5. 4/ 5 ,n V H- am 9, 9 mw .D nl//f////////HH/ lll e b mr o M R 1 M Vl n l l R. E. MANFREDI Filed March8, 1952 HIGH FREQUENCY ELECTRIC DISCHARGE DEVICE oct. 25, 1960 HisAttorney.

general requires a larger structure.

HIGH FREQUENCY ELECTRIC DISCHARGE DEVICE Robert E.,Manfredi,Schenectady, NX., assignor to General Electric Company, a corporation ofNew York Filed Mar. 8, 1952, Ser. No. 275,522

9 Claims. (Cl. 313286) My invention relates. to improved electricdischarge devices `particularly suited for high frequency applications.

,fIn recent years, there has been extensive development .'of highfrequency communication equipment with the result that there has been acontinual demand for electric discharge devices capable of deliveringhigher and higher power outputs at higher and higher frequencies.Successful operation at higher frequencies requires in general that thelead inductance be low, that the interelectrode capacity below, and thatthe spacing between the electrodes be small. Atthe same time, the higherpower requirements require large emission currents which to some extent.makes itnecessary to operate at higher temperatures or to providelarger electrodes. It is readily apparent that kthe requirements forhigh power and high frequency foperation are somewhat inconsistent onewith the other in that the requirements for high frequency in generalrequire a more compact structure, while higher power in Also, attemptsto make more and more compact structures have increased the problemsinvolved in the actual assembly of the various components of electricdischarge devices.

According to an important aspect of my invention, I

provide an improved electric discharge device which is ,operable at highfrequencies, with a high power output vandwhich is readily assembled byproduction methods.

anY improved envelope and terminal construction for a j highfrequencyelectric discharge device.

" Itis a further object of my invention to provide for ltheaccuratehspacing of the electrodes of the device and 'to providerlowinductance from the various electrode ""terminals to the electrodesthemselves. Y Y' It is a'still further object of my invention to providean improved method of assembling and spacing a plurality -of electrodesof anelectric discharge device.

' vIt is another object of my invention to provide a new and improvedcathode assembly, particularly suited for `high,V power, high frequencydischarge devices.

Further objects and advantages of my invention will kbecome apparent asthe following description proceeds, reference being had to theaccompanying drawing, in

which Fig. 1 is an elevational view in section of electric Y dischargedevice embodying my invention; Fig. 2 is an enlarged elevational view,partially broken away, showing the cathode employed in the device ofFig. 1; Fig. 3 is an enlarged side elevational view of a cathodesupporting part shown in Fig. l; and Fig. 4 is a top plan view of thecontrol grid shown in Fig. 1.

Referring now to the drawing, I have shown my inventionembodied in anelectric discharge device particularly 1United States Patent() f It is,an important object of my invention to provide ICC seen that theenvelope includes a generally cylindrical anode structure designated bythe numeral 1, an annular anode terminal 2, an anode to screen gridinsulator in the form of a ceramic cylinder 3, and a screen gridterminal 4. This much of the envelope forms the anode subassembly 5, oneof the major subassemblies of the device, and is completed separatelyfrom the lower subassembly Vdesignated generally by the numeral 6. Thenovel features of the anode are more fully described and claimed in myU.S. Patent No. 2,731,244 issued January 17, 1956, on my applicationSerial No. 275,523, led concurrently herewith and assigned to theassignee of this application.

The lower subassembly includes a control grid support 7 of cylindricalform. The grid supporting cylinder is formed of good conducting materialsuch as copper and as illustrated is of relatively heavy construction. Ascreen grid support and terminal member 8 is bonded to the upper end ofcylindrical insulator 9, which is in turn joined to the lower outsidesurface of the grid support 7 by means of a grid terminal ring 10.

In a similar manner, the cathode and heater terminals are supported inmutually insulated relation from the upper end and inner surface of thegrid support 7. As illustrated, the control grid-cathode insulator 11 isbonded to a metal ring 12 which is brazed at its upper end to Vthe upperand inner surface of the grid supporting cylinder 7. The lower end ofthe insulator 11 is joined to a cylindrical heater and cathode terminalmember 13 provided at its lower end with a circular flange 14 to whichis sealed the cylindrical insulator 15 which insulates the cathode fromthe heater terminal 17. The terminal 17 is joined to the lower end of acentral supporting rod 18 which is in turn sealed to the ceramiccylinder 15 by means of a metal ring (19.

Before describing in detail the elements which make up the envelope ofthe electric discharge device and the manner in which they are assembledin accordance with the present invention, the electrode elements andtheir supports Within the discharge device will be described. Thecathode is in the form of a hollow cylinder 20 substantially closed atits upper end and supported at its lower end from an annular collar 21of refractory metal such as molybdenum. The collar is of smallerdiameter at its lower extremity and is received within a relatively thincathode supporting sleeve 22 which is brazed to the upper end of agenerally cylindrical cathode support 23. The lower end of the member 23is received within and brazed to the cathode terminal 13.

As shown more clearly in Fig. 2, the cathode cylinder 20 is provided atits lower end with slots 24 to facilitate assembly over the header 21.The cathode is also provided with circumferentially extending slots 25and 26 near the lower and upper ends of the sleeve to minimize heat lossfrom the active cathode area to the support at the lower end and to theend cap at the upper end.

The heater for the cathode is in the form` of a double helix 27 oftungsten or other suitable wire. The ends of the heater wire arereceived within longitudinally extending grooves 28 formed in the upperenlarged portion of the collar and secured thereto asby welding (Fig.3). A `Suitable overwinding of wire 29 received in a circumferentialgroove 30 may also be employed -if desired. It will be noted that thecathode sleeve 20 is joined to the large upper portion of the collar 21so that the cathode and the ends of the heater are electrically joinedto the collar 21 and by way of sleeves 22 and 23 to the cathode terminal13. The upper end of the double helix is supported from a central heatersupport rod 31 which is received within and brazed to the larger heatersupport rod 18. The heater rod is maintained -in-a central position.byr'means of a `suitable annular ceramic lmember 32received within'thecylindrical member 23 and held in 3 position by van eyelet 33 brazed tothe heater support rod 18.

The control grid is in the form of a generally hollow cylindricalstructure made up of a plurality of longitudinally extending conductors34 which are secured to a cylindrical collar 35 at .the lower vend Vandwhich are bound together by an overwind of wire 36 `at the upper endthereof. The ends 34 of the individual grid :wires labove the overwindare shorter than the radius of the grid and are bent inwardly in aradial direction in overlapped relationship and resistance Weldedtogether. The grid collar 35 is supported from the upper end of a gridsupporting cone 37 having an outwardly extending flange 38 at the .lowerend thereof resting on an inwardly -directed circular ilange 39 formedintegrally with the grid supporting cyl-inder 7. The grid is secured inposition by means of suitable holding screws 40 extending through anges38 and 39 and an overlying washer 41.

The screen grid is of generally similar construction including the samenumber of longitudinally extending wires 42 bonded to a `screen gridcollar 43 at the lower end thereof and secured together by a wireoverw-ind 44 4at the upper end. The screen grid is not closed at all atits upper end as was the case with the control grid, thus allowingmaximum heat radiation from the top of the control grid. A screen gridsupporting cone 45 is secured to the collar 43 of the screen grid andprovided at its lower end with an outwardly extending flange 46 whichrests upon an inwardly directed ange 47 on an annular screen gridsupport 48 bonded to the inner surface of the cylindrical screen gridterminal member 8.

In order to provide for easy rotational adjustment of the screen gridrelative to the control grid for the purpose of aligning the screen gridwires 42 with the control grid wires 34, the screen grid cone 45 issecured to the flange 47 by means of a collar 49 recessed on its lowerand inner surface to receive the outwardly extending flange 46 of thescreen grid cone. The collar is secured by suitable screws 49 to thescreen grid supporting flange 47, and, as will be readily apparent,permits the easy rotational adjustment of the screen grid cone 45.

It will also be noted that the supporting cones 37 and 45 for thecontrol grid and screen grid extend in closely spaced relation over anextended area and in this way provide very close coupling between thesetwo grids with respect to high frequency voltages. In this Way, bothgrids may be maintained readily at the same high frequency potential.

The general organization and construction of the various components ofan electric discharge device embodying my invention have been described.A more detailed description of some of the component elements and themanner in which they are assembled will serve to further emphasizecertain of the features and advantages of my invention. It should bepointed out at this time that all of the bonds between the ceramicmembers and the metal members are accomplished in a Single brazingoperation along with the making of the joints between the various metalelements of the envelope Iby use of a suitable brazing material such asa silver solder. The brazing to the ceramic is made possible by theprior metalizing of the ceramic in the region to be bonded. While manymethods have been suggested in the prior art for metalizing ceramicmembers for this purpose, a particularly effective method involves theapplication of a powdered mixture of manganese and molybdenum to theregions to be bonded and heating the ceramic members thus coated in ahydrogen atmosphere. This coating may be built up by one or more platingsteps, if desired, prior to the brazing operation. This method ofmetalizing and bonding to ceramics is described in detail and claimed incopending Nolte application, Serial No. 238,871, liled July 27, 1951,and assigned to the assignee of this application.

As previously pointed out, the lower portion of the envelope isassembled as a separate subassembly 6. This portion of the envelopeincludes screen grid terminal member 8, ceramic cylinder 9, sealing ring10, grid support 7, sealing ring 12, ceramic cylinder 11, sealing ring13, ceramic cylinder 15, sealing ring 19, and heater support 18. Inaddition to these envelope and terminal members, this subassemblyincludes the cathode supports 22, 23, the spacer 32 and eyelet 33; also,the heater rod 31 which is brazed as a preliminary step to the heaterrod 18.

The parts enumerated above are assembled in a suitable brazing fixturein an inverted position with respect to that illustrated in the drawing.The fixture is provided with suitably spaced supporting surfaces forengaging the following surfaces of the subassembly: the surface 50 ofthe screen grid terminal, the supporting liange 47 of the screen support48, supporting flange 39 of the grid support 7, the upper end of thecathode supporting cylinder 22, and the end of the heater supporting rod31. It will be noted that when these surfaces are supported in aninverted position from that shown in the drawing, al1 of the remainingparts of the subassembly are self-supporting. To that end, the sealingrings including a portion of the screen grid terminal are indented atwhat is the upper edge of the ceramic, as shown in the drawing. Theseindentations are shown as providing shoulders 51, 52 and 53, forexample. The other sealing rings 10, 13 and 19 are inherently supporteddue to the decreasing dimensions of these members in the direction ofthe heater rod 18. It will be appreciated that the various brazed jointsare made by positioning suitable solder rings or washers adjacent thejoints as the subassembly is positioned on the iixture prior to thebrazing operation.

It will be noted from an inspection of the drawing and the descriptionthat has preceded that the ceramic members are entirely free of anysubstantial stress due to the contact pressure that may be applied tothe various terminals of the device. The anode contact is made with theouter flange 54 spaced from the anode-screen grid insulator 3. In asimilar manner, the screen grid contact is made to the outer flange 55of screen grid terminal 4. The remaining contacts are made againstportions of the envelope which are supported by rigid metal members; thecontrol grid contact being made to the sealing member 10 on the outersurface of the grid support 7, cathode contact being made to the ring 13supported by the cathode support 23, and the heater terminal being madeto a solid contact 17 at the end of the heater support rod 18.

It will be apparent from la consideration of the foregoing descriptionthat the invention provides, by virtue of the shape of the variousmembers employed and the use of ceramic members which do not softenduring the sealing process, a structure in which the relative positionsare readily maintained and in which the lead-in inductance to thevarious electrodes is kept at a minimum. It will be noted that byconnecting the cathode supports to the upper and inner surfaces of thegrid supports, while the control grid-screen grid insulator is connectedto the lower and outer surface of the control grid support, a muchshorter structure is obtained. The final joint of the envelope structureis made at the lower edge of the two screen grid terminal members 4 and8 and is designated by the numeral 56. After assembly, the tube isexhausted through a suitable exhaust tubulation 57 which is shown asprotected by the surrounding cap 58.

While I have described a particular embodiment of my invention, it willbe apparent to those skilled in the art that changes and modificationsmay be made Without departing from my invention in its broader aspects,and I aim `therefore in the appended claims to cover all such changesand modifications as fall within the true spirit and scope of myinvention.

said support, a circular'flange of larger diameter and an intermediateportion connecting said ilanges, a hollow cylindricalceramic insulatorreceived within said flange of larger diameter at one end and engagingsaid intermediate portion anda1.secoi1d sealing ring .having a circularflange encircling and bonded to lan outer surface of the said ceramicinsulator at the opposite end thereof, said second ring having aninwardly projecting shoulder extending inwardly over and engaging theend of said insulator to position said ring relative to said insulator.

2. An envelope structure for an electric discharge device comprising apair of metal sealing rings each including relatively smaller and largerconcentric and axially displaced cylindrical anges joined by afrusto-conical section, an annular' ceramic insulator, the smallerilange of one of said rings encircling one end of said insulator and thelarger flange of the other of said rings encircling the other end ofsaid insulator, said last-mentioned iianges being bonded to saidinsulator, a pair of hollow cylindrical conductive electrode supports,one of said supports comprising a wall section of said envelope andhaving an inner diameter larger than the outer diameter of saidinsulator and the other of said supports having an outer diametersmaller than the inner diameter of said insulator, the larger llange ofsaid one of said rings and the smaller flange of said other of saidrings being bonded respectively to an inner surface of said rstelectrode support and to an outer surface of said second electrodesupport, and a third sealing ring having relatively smaller and largerconcentric and axially displaced cylindrical flanges joined by afrusto-conical section, said smaller ilange of said third sealing ringbeing positioned about and bonded to the outer surface of said rstelectrode support.

3. In combination, a hollow cylindrical electrode support, a metalsealing ring having a pair of relatively smaller and larger concentricand axially displaced cylindrical flanges, the larger of said flangesbeing bonded to a surface of said electrode support, an annular ceramicinsulator, said smaller flange encircling said insulator at one endthereof and being bonded thereto, a second metal sealing ring includinga pair of relatively smaller and larger concentric and axially displacedvcylindrical lianges joined by an intermediate cylindrical portion, thelarger flange of said second ring encircling the other end of saidceramic insulator and being bonded thereto, a second hollow cylindricalelectrode support, said intermediate portion of said second ringencircling said second electrode support and being bonded thereto, athird electrode support, said smaller flange of said second ringencircling said third electrode support and being bonded thereto.

4. In combination, a hollow cylindrical electrode support, a metalsealing ring constructed of relatively thinner material than saidelectrode support and having a pair of relatively smaller and largerconcentric and axially displaced cylindrical llanges extending inopposite directions from an intermediate portion olf said ring, saidring being disposed in said electrode support and having said largerllange bonded to the inner surface of said support, an annular ceramicinsulator havin-g an outer diameter substantially equal to the innerdiameter of the smaller of said flanges, said smaller flange encirclingsaid insulator at one end thereof, and inwardly projecting annular ribat the junction of said intermediate portion and the smaller of saidllanges for positioning said ceramic insulator with respect to saidsealing ring.

5. A cathode and heater assembly comprising a generally cylindricalsupport including a pair of longi- ,"tudinally extending recesses onoppositesides of said support,v arheater element having end portionsreceived ,respectively in said recesses, a hollow cylindrical cathodesurrounding said heater, said cathode having a plurality ofcircumferentially extending recesses adjacent opposite ends thereof forminimizing the transfer of heat to the closed end thereof and to said.support. f

6. A athod'e'rheater assembly comprising a generally cylindricalsupport, a pair of longitudinally extending leesses; onrs'aidwsupportLaheater` element having end portions received respectively in saidrecesses, a hollow cylindrical cathode member open at one end, saidsupport being received Within the open end of said cathode and bondedthereto with said cathode surrounding said heater, said cathode having aplurality of circumferentially extending recesses adjacent said open endto minimize the transfer of heat to said support.

7. An electric discharge device envelope comprising a rigid cylindricalmetal electrode support member constituting a Wall section of saidenvelope extending reentrantly in one end of said envelope, a pair lofmetal sealing rings of a relatively thinner construction than saidsupport member and each including relatively smaller and largerconcentric and axially displaced cylindrical ilanges connected by asubstantially frustoaconical portion, the smaller ange of one ringhaving the same diameter as the larger ange of the other ring, anannular ceramic insulator, the smaller ilange of one of said ringsencircling one end of said insulator and the larger flange of the otherof said rings encircling the other end of said insulator, said lastmentioned ilanges being bonded to an outer surface of said insulator,and said seal-ing rings and insulators being reentrantly positioned insaid support member with the largest of said flanges bonded to the innersurface of said support member adjacent the inner end thereof.

8. An electric discharge device comprising an envelope, electrodes inthe envelope including an anode, grid and cathode, a first ceramicsection included in the wall of said envelope, a tubular metal gridterminal having a flange encircling and bonded to the lower end of saidrst ceramic section, a cathode stem comprising a metal stem membercoaxial with the grid terminal, a metal supporting sleeve having lasmaller outer diameter than the inner diameter of said iirst ceramicsection and extending in said first ceramic section and said gridterminal, said sleeve having an edge registering with and being bondedto the lower edge of said grid terminal, a second ceramic sectioninterposed between said stem member and said supporting sleeve, saidsecond ceramic section having an inner diameter larger than the outerdiameter of said stem member, metallic bonds uniting said second ceramicsection to said stemmember and to said sleeve outwardly of the inner endof said sleeve whereby said inner end thereof is wholly disposedinternally of said envelope, land said internally disposed end of saidsleeve having a flange supporting said grid electrode.

9. An electric discharge device comprising an envelope, electrodes insaid envelope including an anode, a pair of grids and a cathode, a rstcenamic section included in the wall of said envelope, a pair of axiallydisplaced tubular metal grid terminals on said envelope, said irstceramic section having the opposite ends thereof positioned in landbonded to the opposed ends of said grid terminals, a pair of coaxiallyspaced grid supports in said envelope, one of said supports being bondedto the internal surface of one of said grid terminals, the other of saidsupports comprising a metal sleeve of smaller diameter than said firstterminal and constituting a wall section of said envelope extending inone end of said envelope, said sleeve having an edge registering with v7the lower edge of the other of 4said grid terminals, a cathode stemcomprising va metal Vstern member coaxial with the grid terminal, asecond cenamic section having an outer diameter less vthan the innerdiameter of Asaid support sleeve and an inner diameter larger than theouter diameter of said stem member, and sealing rings joining the innerend -of saidsecond ceramic section to the inner surface of said supportsleeve andthe outer surface of said stem member.

References Cited in the file of this patent UNITED STATES PATENTS2,445,237 Stone July 13, 1948 '8 2,517,334 Murdock Aug. 1, 19502,580,988 `Anderson Jan. 1, 1952 2,644,907 Drieschman et al. uly 7, 1953'.5 FOREIGN PATENTS 773,488 France Sept. 3, 1934 OTHER REFERENCESElectronic Engineering, August 1941, pages 343, 344, '10 and 376.

